1. Field of the Invention
The present invention relates to an air actuated hydraulic pump, more particularly an air actuated hydraulic pump, which is equipped with elongated air passages, a manually operated vent valve assembly, and a pilot operated guided poppet valve comprised of several parts in detachable connection, and which is structured so that noise is reduced when working.
2. Brief Description of the Prior Art
Hydraulic jacks are used for raising objects to be repaired and maintained. Early hydraulic jacks need to be operated with hands moving a lever or feet pressing a pedal therefore the objects are raised at relatively low speed and the operation costs a lot of labor; hydraulic oil is released to lower the lifted objects.
Other conventional hydraulic jacks, such as are disclosed in Taiwan Patent no. 79213367 and no. 80210290, are equipped with an air motor so that hydraulic oil can be pumped with pressured air causing reciprocation of a piston. However, conduits have to be provided in the air motors for air communication of one room with another, causing trouble in manufacturing and assembling. And, such conduits are prone to be damaged, and need repair, which would also cost relatively much labor.
Taiwan Patent no. 82201954 disclosed an air actuated hydraulic jack to overcome the above disadvantages to the conduits of the air motor. However, this jack is found to have disadvantages as followings:    1. Two opposing air passage grooves are formed on an inner side of a tube, within which a piston of the air motor is moved, by means of striking the inner side of the tube with pressing machines. The shaping process is difficult to carry out because the direction of striking is from inside of the tube to outside.    2. The roundness of the tube will be changed due to the shaping process, badly affecting the performance of the air motor.    3. The air motor is equipped with a piston, which is comprised of parts inseparably connected together. Therefore, the whole piston has to be replaced with a new one even if only one of the parts is damaged or has worn down, making maintenance cost a burden on the user.    4. The air motor is not equipped with a vent valve assembly, and will produce loud noise when working.